Resources for Yevamos daf 94
1. The גמרא says in the name of רב that the better דרשה from the פּסוק of “ואשה גרושה “מאישה is to learn that a woman who received a גט that says she is divorced from her husband but she isn’t allowed to marry anyone else is enough to פּסול her לכהונה as a ריח הגט. It would seem clear from the simple reading of the גמרא that this is a דרשה דאורייתא for if it wasn’t רב wouldn’t have called it the better דרשה to make. However, the רמב"ם in הלכות גירושין פּרק י׳ הל׳ א says that if a woman received such a גט she is only פּסול לכהונה מדרבנן. That means the דרשה is only an אסמכתא. The לחם משנה there asks that this would seem to be against our גמרא. The ערוך לנר answers that our גמרא is actually a proof to the רמב"ם ! He says that theרמב"ם understood from the משמעות of the גמרא that it can’t be that both דרשות are true מדאורייתא. Rather, only one דרשה can be made. Therefore, since no one argues in the משנה, it must be that we pasken like the דרשה in the משנה. The קובץ הערות in סימן ס"ו אות ב says a different answer which is a very interesting idea. He suggests that theרמב"ם learned that the גמרא was just telling us that there is a concept of מדאורייתא שיור בגט. However, in practice there is no היכי תימצא where it can play out since getting a divorce without being permissible to any other person is not a גט מדאורייתא. He brings a proof to this unusual notion from a ר"ן in הכותב who says that we learn from a דרשה that there is no אונאה when selling שטרות even though there is no way to sell שטרות מדאורייתא. We see the תורה can comment on things that in practice have no way of happening מדאורייתא and the רבנן make their דינים based on that.
2. The גמרא discusses whether an עד אחד is believed to allow a woman to marry without having יבום וחליצה. The מרחשת in סימן י"ד אות ב-ג brings the נודע ביהודה who says that the איסור of יבמה לשוק is not a דבר שבערוה. The מרחשת asks how he could say that when it should be clear from our סוגיא that it is--If it wasn’t a דבר שבערוה, why would our גמרא even have a ספק whether an עד אחד is believed? An עד אחד is always נאמן באיסורין! He answers that in our case we have two חזקות which say she should not be מותרת לשוק: one is the חזקת חי of the יבם and the other is the חזקת איסור לשוק. He explains that even though an עד אחד is believed even in a case of איתחזק איסורא, when there are two חזקות לאיסור then he is not believed. The reason two חזקות can beat an עד אחד is as follows: the ריב"ש in his תשובות in סימן שע"ט says that two חזקות is equivalent to a רוב. The שב שמעתתא in שמעתתא ו׳ אות ז says that עד אחד is not believed against a רוב. Therefore, even if you were to say that יבמה לשוק is not a דבר שבערוה, it would still be a question if an עד אחד would be believed to say she could be מותרת לשוק since the עד אחד is going uo against a רוב.
The משנה says that a man’s wife and brother-in-law went away and news arrived that they had both died and the man who stayed at home married his wife’s sister and then the wife came back. רש"י in ד"ה וגיסו says that this story happened based on the testimony of an עד אחד. The מרומי שדה asks how the man was allowed to believe an עד אחד to marry an ערוה to him! After all, אין דבר שבערוה פּחות משנים! He answers that since the עד also said the wife’s sister’s husband died as well, since he is believed to say the brother-in-law died, we believe him to say that the man’s wife died as well. He explains that רש"י holds that really מדאורייתא an עד אחד is believed since it is a מילתא דעבידי לאגלויי, and it’s just מדרבנן that we need two עדים. Therefore, when there is this “מיגו” of sorts he is believed on both.
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